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Map depicting incidence and spread of tar spot of corn, caused by Phyllachora maydis, in the United States from 2015 to 2019.
Source publication
Tar spot on corn, caused by the fungus (Phyllachora maydis Maubl. [Phyllachorales: Phyllachoraceae]), is an emerging disease in the United States. In 2018 and 2019, significant but localized epidemics of tar spot occurred across the major corn producing region of the Midwest. After being first detected in 2015, tar spot was detected in 135 and 139...
Context in source publication
Context 1
... and 308 counties in 2019 (Table 1). First detection of the disease ranged from 26 June in Illinois (IL) to 1 October in Ohio (OH) in 2018 and 12 July in Indiana (IN) to 23 October for Missouri (MO) in 2019 ( Table 1). The counties confirmed by state ranged from 46 in IL to 4 in Florida (FL) in 2018 and 87 in Iowa (IA) to 3 in MO in 2019 (Table 1; Fig. 1). In 2019, tar spot was detected ...
Citations
... This crop disease was first confirmed in the continental United States (U.S.) in 2015 [1]. As of July 2023, tar spot had been documented in 18 states and Ontario, Canada, and significant grain-yield losses were reported across corn-producing regions over multiple years [2][3][4]. The recent emergence of the disease and the dearth of information have made the disease a significant issue, prompting the need for studies to understand the interactions of corn with P. maydis and develop tar spot management strategies. ...
Background:
Tar spot of corn is a significant and spreading disease in the continental U.S. and Canada caused by the obligate biotrophic fungus Phyllachora maydis. As of 2023, tar spot had been reported in 18 U.S. states and one Canadian Province. The symptoms of tar spot include chlorotic flecking followed by the formation of black stromata where conidia and ascospores are produced. Advancements in research and management for tar spot have been limited by a need for a reliable method to inoculate plants to enable the study of the disease. The goal of this study was to develop a reliable method to induce tar spot in controlled conditions.
Results:
We induced infection of corn by P. maydis in 100% of inoculated plants with a new inoculation method. This method includes the use of vacuum-collection tools to extract ascospores from field-infected corn leaves, application of spores to leaves, and induction of the disease in the dark at high humidity and moderate temperatures. Infection and disease development were consistently achieved in four independent experiments on different corn hybrids and under different environmental conditions in a greenhouse and growth chamber. Disease induction was impacted by the source and storage conditions of spores, as tar spot was not induced with ascospores from leaves stored dry at 25 ºC for 5 months but was induced using ascospores from infected leaves stored at -20 ºC for 5 months. The time from inoculation to stromata formation was 10 to 12 days and ascospores were present 19 days after inoculation throughout our experiments. In addition to providing techniques that enable in-vitro experimentation, our research also provides fundamental insights into the conditions that favor tar spot epidemics.
Conclusions:
We developed a method to reliably inoculate corn with P. maydis. The method was validated by multiple independent experiments in which infection was induced in 100% of the plants, demonstrating its consistency in controlled conditions. This new method facilitates research on tar spot and provides opportunities to study the biology of P. maydis, the epidemiology of tar spot, and for identifying host resistance.
... Mottaleb et al. (2019) revealed that Phyllachora maydis causing tar spot disease in maize, can survive on dry leaves and also on other parts of plants, such as the husks of maize ears etc. In plants with a high attack of tar spot disease, we also found the fruiting body of Phyllachora on leaf midribs and husks or seed coats (Kleczewski et al., 2020) as well can be calculated using the Horsfall & Barratt formula (1945) using the score data from the list above. Scoring data is not displayed in this report. ...
The sorghum (Sorghum bicolor) plant is highly tolerant and adapted to drought. It has the potential to be developed and planted on marginal land in Indonesia. Tar spot disease is one of the obstacles to sorghum cultivation. In Indonesia, there is no report yet about this disease, especially on sorghum. To achieve optimal disease management, information on disease incidence and severity levels, as well as pathogen tar spot disease identification, are required. The aims of this study were to morphologically identify the pathogen and determine the level of incidence and severity of tar spot in sorghum cultivation areas in Bogor Regency, Gunung Kidul Regency, and West Lombok Regency. The disease observations were carried out on 17 sorghum varieties from the three areas with no experimental design. The results of the observation of the tar spot disease incidence in 17 varieties of sorghum from Bogor, Gunung Kidul, and West Lombok were 100%. The level of tar spot disease severity varied from 32.4% in the Latu Keta sorghum variety to the highest of 87.9% in the Samurai sorghum variety. The macroscopic and microscopic observation results of tar spot on sorghum plants showed that the cause of the tar spot disease was the Phyllachora fungi. This is the first report of a tar spot on sorghum caused by Phyllachora sp. in Indonesia.
... Mottaleb et al. (2019) revealed that Phyllachora maydis causing tar spot disease in maize, can survive on dry leaves and also on other parts of plants, such as the husks of maize ears etc. In plants with a high attack of tar spot disease, we also found the fruiting body of Phyllachora on leaf midribs and husks or seed coats (Kleczewski et al., 2020) as well can be calculated using the Horsfall & Barratt formula (1945) using the score data from the list above. Scoring data is not displayed in this report. ...
The sorghum (Sorghum bicolor) plant is highly tolerant and adapted to drought. It has the potential to be developed and planted on marginal land in Indonesia. Tar spot disease is one of the obstacles to sorghum cultivation. In Indonesia, there is no report yet about this disease, especially on sorghum. To achieve optimal disease management, information on disease incidence and severity levels, as well as pathogen tar spot disease identification, are required. The aims of this study were to morphologically identify the pathogen and determine the level of incidence and severity of tar spot in sorghum cultivation areas in Bogor Regency, Gunung Kidul Regency, and West Lombok Regency. The disease observations were carried out on 17 sorghum varieties from the three areas with no experimental design. The results of the observation of the tar spot disease incidence in 17 varieties of sorghum from Bogor, Gunung Kidul, and West Lombok were 100%. The level of tar spot disease severity varied from 32.4% in the Latu Keta sorghum variety to the highest of 87.9% in the Samurai sorghum variety. The macroscopic and microscopic observation results of tar spot on sorghum plants showed that the cause of the tar spot disease was the Phyllachora fungi. This is the first report of a tar spot on sorghum caused by Phyllachora sp. in Indonesia.
... Mottaleb et al. (2019) revealed that Phyllachora maydis causing tar spot disease in maize, can survive on dry leaves and also on other parts of plants, such as the husks of maize ears etc. In plants with a high attack of tar spot disease, we also found the fruiting body of Phyllachora on leaf midribs and husks or seed coats (Kleczewski et al., 2020) as well can be calculated using the Horsfall & Barratt formula (1945) using the score data from the list above. Scoring data is not displayed in this report. ...
The sorghum (Sorghum bicolor) plant is highly tolerant and adapted to drought. It has the potential to be developed and planted on marginal land in Indonesia. Tar spot disease is one of the obstacles to sorghum cultivation. In Indonesia, there is no report yet about this disease, especially on sorghum. To achieve optimal disease management, information on disease incidence and severity levels, as well as pathogen tar spot disease identification, are required. The aims of this study were to morphologically identify the pathogen and determine the level of incidence and severity of tar spot in sorghum cultivation areas in Bogor Regency, Gunung Kidul Regency, and West Lombok Regency. The disease observations were carried out on 17 sorghum varieties from the three areas with no experimental design. The results of the observation of the tar spot disease incidence in 17 varieties of sorghum from Bogor, Gunung Kidul, and West Lombok were 100%. The level of tar spot disease severity varied from 32.4% in the Latu Keta sorghum variety to the highest of 87.9% in the Samurai sorghum variety. The macroscopic and microscopic observation results of tar spot on sorghum plants showed that the cause of the tar spot disease was the Phyllachora fungi. This is the first report of a tar spot on sorghum caused by Phyllachora sp. in Indonesia.
... The Corn Disease Working Group in the USA collated occurrence data (workflow Step I) of black spot of maize (Phyllachora maydis), produced spatially explicit visualization tools (Steps V & VI) for stakeholders (e.g. growers) via social media (Kleczewski et al., 2020; Table 1) and allowed reporting via a web-hosted platform that automatically generated and shared maps in real time. This provided in-season knowledge of disease movement and spread at temporal scales that were helpful to growers (Kleczewski et al., 2020). ...
... growers) via social media (Kleczewski et al., 2020; Table 1) and allowed reporting via a web-hosted platform that automatically generated and shared maps in real time. This provided in-season knowledge of disease movement and spread at temporal scales that were helpful to growers (Kleczewski et al., 2020). This concept is also demonstrated by the Soybean Rust -Pest Information Platform for Extension and Education (SBR-PIPE) program, a collaboration to monitor the distribution and impacts of soybean rust (Phakopsora pachyrhizi) in North America (Hershman, Sikora & Giesler, 2011;Sikora et al., 2014). ...
Invasive alien species (IAS) are a rising threat to biodiversity, national security, and regional economies, with impacts in the hundreds of billions of U.S. dollars annually. Proactive or predictive approaches guided by scientific knowledge are essential to keeping pace with growing impacts of invasions under climate change. Although the rapid development of diverse technologies and approaches has produced tools with the potential to greatly accelerate invasion research and management, innovation has far outpaced implementation and coordination. Technological and methodological syntheses are urgently needed to close the growing implementation gap and facilitate interdisciplinary collaboration and synergy among evolving disciplines. A broad review is necessary to demonstrate the utility and relevance of work in diverse fields to generate actionable science for the ongoing invasion crisis. Here, we review such advances in relevant fields including remote sensing, epidemiology, big data analytics, environmental DNA (eDNA) sampling, genomics, and others, and present a generalized framework for distilling existing and emerging data into products for proactive IAS research and management. This integrated workflow provides a pathway for scientists and practitioners in diverse disciplines to contribute to applied invasion biology in a coordinated, synergistic, and scalable manner.
... In 2015 tar spot was reported for the first time in the United States (Ruhl et al., 2016). Since its appearance in the Midwest, tar spot has been identified in the following states: Indiana, Illinois, Iowa, Wisconsin, Michigan, Florida, Ohio, Minnesota, Missouri, and Pennsylvania, Kentucky, Georgia, and several provinces in Ontario (Bissonnette, 2015;Dalla Lana et al., 2019;Kleczewski, Plewa, et al., 2020;Malvick et al., 2020;McCoy et al., 2018). The current status and historical spread of tar spot at a county level can be viewed through the Integrated Pest Management for Pest Information Platform for Extension and Education monitoring system (ipmPIPE, https://corn.ipmpipe.org/tarspot/). ...
Tar spot of maize (Zea mays L.), caused by the obligate biotroph Phyllachora maydis Maubl., is an emerging disease in the United States and Canada, and the identification of sources of resistance for tar spot will enable the development of resistant hybrids. In 2019 and 2020, 25 accessions from the germplasm enhancement of maize (GEM) project containing exotic introgressions in elite backgrounds were evaluated in nine environments for tar spot severity. Environmental conditions had a major influence on disease development, as tar spot severity varied across locations with only four of the nine locations showing moderate to high levels of disease. In five environments, disease levels were low and disease severity data was not collected or used. Accessions were visually evaluated for tar spot during reproductive growth stages in three environments and during vegetative growth stages in one environment. There was a strong correlation between resistance to P. maydis across locations where accessions were evaluated in reproductive growth stages. Two accessions, GEMS‐0066 and GEMS‐0226, were the most resistant and could prove useful for tar spot resistance breeding. These accessions are publicly available and able to be directly used in breeding programs.
Tar spot, caused by Phyllachora maydis, is an emerging disease of corn in the United States. Stromata of P. maydis are sometimes surrounded by necrotic lesions known as fisheyes and were previously reported to be caused by the fungus Microdochium maydis. The association of M. maydis with fisheye lesions has not been well documented outside of initial descriptions from the early 1980s. The objective of this work was to assess and identify Microdochium-like fungi associated with necrotic lesions surrounding P. maydis stromata using a culture-based method. In 2018, corn leaf samples with fisheye lesions associated with tar spot stromata were collected from 31 production fields across Mexico, Illinois, and Wisconsin. Cultures of pure isolates collected from Mexico believed to be M. maydis were included in the study. A total of 101 Microdochium/ Fusarium-like isolates were obtained from the necrotic lesions, and 91% were identified as Fusarium spp., based on initial ITS sequence data. Multi-gene (ITS, TEF1-α, RPB1, and RPB2) phylogenies were constructed for a subset of 55 isolates; Microdochium, Cryptostroma, and Fusarium reference sequences were obtained from GenBank. All the necrotic lesion isolates clustered within Fusarium lineages and were phylogenetically distinct from the Microdochium clade. All Fusarium isolates from Mexico belonged to the F. incarnatum-equiseti species complex, whereas >85% of the U.S. isolates grouped within the F. sambucinum species complex. Our study suggests that initial reports of M. maydis were misidentifications of resident Fusarium spp.
[Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Tar spot, caused by Phyllachora maydis, is the most significant disease of corn in the north central United States. Elucidating an integrated management approach to protect grain yield is a high priority. The integration of tillage, hybrid, and fungicide application on tar spot severity, canopy greenness, and grain yield was assessed in Indiana in 2019, 2020, and 2021. A split-plot arrangement of two tillage treatments as main plots with factorial arrangement of subplots with three hybrids (tar spot susceptible and two partially resistant) and fungicide application (propiconazole +benzovindiflupyr +azoxystrobin) were evaluated. Further, a multistate study comparing two hybrids (susceptible and partially resistant) and fungicide application (propiconazole +benzovindiflupyr +azoxystrobin) was conducted in Indiana, Michigan, and Wisconsin in 2020. This research demonstrates that partially resistant hybrids with a sAUDPC of 2.5 and 3.0 had significantly less tar spot than a susceptible hybrid with a sAUDPC of 10.1 and increased canopy greenness rating of 48.1 and 51.5% which were significantly higher than the susceptible hybrid at 13.0% at maturity. Tar spot severity was further reduced and canopy greenness increased with a fungicide application in the susceptible hybrid. These results suggest that partial resistance alone may be used to manage tar spot. Yields did not differ significantly across hybrids with or without a fungicide application. However, a general trend of preserved yield potential was observed in the treatments with fungicide, indicating that knowledge of genetics and yield potential will be necessary to achieve the most benefit from partially resistant hybrids and judicious fungicide applications.
Tar spot of corn is an emerging plant disease in the continental U.S. and Canada caused by the fungal pathogen Phyllachora maydis Maubl. Tar spot has been known to occur in Mexico, the Caribbean, and Central and South America since the early-mid 1900s. In 2015, it was reported for the first time in the continental U.S. Since that time, tar spot has spread across corn-producing areas in the U.S. with epidemics as recent as 2021 resulting in significant yield losses. Although tar spot has been known to affect corn for over a century in the Americas, the biology of the pathogen, etiology, and epidemiology of the disease are not well understood. Additionally, symptoms and signs of tar spot resemble other foliar diseases and abiotic disorders of corn, which may lead to misdiagnosis. In this paper, we provide a brief description of current knowledge about tar spot of corn, including pathogen taxonomy, host range, symptoms and signs, specimen storage, pathogenicity testing, diagnostic protocols, and geographic distribution. This information will be useful to diagnosticians, researchers, and other professionals working with this disease.
Tar spot is a major foliar disease of corn caused by the obligate fungal pathogen Phyllachora maydis, first identified in Indiana in 2015. Under conducive weather conditions, P. maydis causes significant yield losses in the U.S. and other countries constituting a major threat to corn production. Relatively little is known about resistance to tar spot other than a major quantitative gene that was identified in tropical maize lines. To test for additional sources of resistance against populations of P. maydis in North America, twenty-six parental inbred lines of the Nested Associated Mapping (NAM) population were evaluated for tar spot resistance in Indiana in replicated field trials under natural infection for 3 years. Tar spot disease severity was scored visually using a 0 to 100 % scale. Maximum disease severities (MDS) for tar spot scoring at reproductive growth stage ranged from 0 to 48.3 % with 0% being most resistant and 48.3% being most susceptible. Nine inbred lines were resistant to P. maydis with MDS ranging from 0 to 5.0%, six were moderately resistant (5.2 to 10.6% MDS), two were moderately susceptible (11.7 to 26.0% MDS) and the remaining eight inbred lines were rated as susceptible (30.0 to 48.3% MDS). There was some variability between years, due to higher disease pressure after 2019. Inbred B73, the common parent of the NAM populations, was rated as susceptible with MDS of 30.0%. The nine highly resistant lines provide a potential source of new genes for genetic analysis and mapping of tar spot resistance in corn.
